In the processing of tubular knitted fabrics, it is conventional to perform a number of operations, such as washing, bleaching, dyeing, etc. with the fabric in the form of an elongated tubular web. Knitted fabric has notoriously poor geometric stability, particularly when wet, and thus typically becomes considerably elongated and correspondingly reduced in width during the various processing operations that are normally required. Accordingly, as one of the normal finishing operations, it is typical at one or more stages to cause the tubular fabric to be advanced over a spreader device, which distends the fabric laterally to a predetermined width, ideally close to the "natural" width of the knitted fabric. While thus laterally distended, the fabric may be moistened by steaming and then calendered by opposed pressure rolls. In some cases, the fabric at this stage may be subjected to mechanical compressive preshrinkage operations. Representative forms of such spreader devices are disclosed in, for example, the Andrew P. Cecere U.S. Pat. No. 4,173,812 and/or the Robert Frezza U.S. Pat. No. 4,192,045, both assigned to Samcoe Holding Corporation. These and many other forms of spreader devices for tubular knitted fabric utilize a pair of opposed edge drive rolls, which engage the opposite sides of the spreader device. The tubular fabric, passing over the spreader, is gripped between the side edges of the spreader frame and the opposed edge drive rolls. In most cases, the spreader is provided with internal propeller belts, which engage the fabric tube by its internal edges and convey it forwardly. These belts are driven indirectly by the externally driven edge drive rolls, which press through the fabric edges and drive internal belt pulleys frictionally, through the intervening fabric wall.
Propeller-spreader mechanisms of the type generally described above have been widely and successfully used for many years. Nevertheless, with respect to certain especially "sensitive" fabrics, particularly those designed for outerwear garments, the pressure of the edge rolls on the fabric, where the spreader frame is supported by the edge rolls and the internal belts are engaged and driven, is enough to mark the fabric and reduce its quality and its ultimate saleability.
Numerous efforts have been made in the past to construct the spreader apparatus in such manner as to enable the internal belts of the spreader to be properly driven, while at the same time minimizing the tendency of the equipment to mark the processed fabric, particularly the more sensitive, darker shades of outerwear fabric. A theoretically interesting approach to this end is reflected in the Johnson U.S. Pat. No. 2,507,599, in which provision was made for magnetically coupling an internal belt drive mechanism of a spreader apparatus to a magnetic external drive arrangement. Theoretically, at least, this enabled the internal fabric-engaging belts to be driven without the necessity of establishing driving contact through the fabric wall. The apparatus of the Johnson patent nevertheless utilized edge rolls, much in the nature of conventional, externally driven edge drive rolls, for supporting the spreader frame by its edges, and inherently imposing some degree of concentrated pressure at the fabric edges, carrying the possibility of edge marking. Insofar as the applicant is aware, the mechanism of the Johnson patent did not achieve commercial success. The Hogendyk U.S. Pat. No. 3,955,251 employed magnetic devices as the principal means of positioning the spreader. No internal drive means were provided for, however.
In accordance with the present invention, a novel and greatly improved form of spreader-propeller apparatus is provided, which utilizes certain of the basic concepts illustrated in the before mentioned Johnson patent, for the driving of internal spreader belts by means of magnetic coupling, but which constitutes a significant improvement over the prior art apparatus in respect of its ability to deliver processed fabric free of undesirable marking. To this end, magnetically coupled, external drive means are provided, normally positioned on one side of the spreader frame, directly opposite and cooperatively coupled with magnetic internal drive pulleys for the spreader frame internal belts. In accordance with one aspect of the invention, the spreader frame support structure includes a pair of transverse support rollers, typically full width, arranged in straddling relation to the external magnetic drive elements. These across-the-width support rollers define a common plane spaced just slightly above the upper surfaces of the magnetic drive elements and provide for the central support of the spreader frame with the internal belt-driving discs in closely spaced, magnetically coupled relation to the external drive discs. The spaced support rollers are driven in synchronism with the external drive discs such that, when fabric is being advanced over the spreader, it is essentially not affected by the support rollers. Further, the support rollers are arranged to engage the fabric over a broad, flat surface, rather than at its edges, making it possible to spread the supporting force over a relatively great area, so as to maintain unit pressures at a practical minimum. Additionally, supporting the spread fabric across one of its broad faces, avoids problems, inherent at the edges, arising from the fact that the fabric does not present a flat surface in the edge regions. As a result, it is more difficult to avoid high unit pressure at the edges, and it may also be difficult to avoid some rubbing of the fabric. The use of grooved rolls, for example, at the edges results in different surface areas of the grooved rolls having different surface speeds, such that not all portions of the grooved rolls can be maintained in non-slipping contact with a curved edge surface of the fabric.
In accordance with another aspect of the invention, the propeller-spreader apparatus, supported by across-the-width, driven rollers, may be positioned effectively in the upstream-downstream directions, and also in the width directions, exclusively by means of the magnetic coupling elements, without requiring addition rollers or other positioning means to make physical engagement with the spreader apparatus. Further, in this respect, under certain conditions, it is possible to utilize the magnetic coupling effect of the external magnetic drives to effect width adjustment of the spreader apparatus, although for most fabrics it is necessary or desirable to provide for more positive width setting of the spreader frame.
For a more complete understanding of the invention, and a more detailed description of the above and other features and advantages thereof, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings.